Method of manufacturing a food container

ABSTRACT

A method of commercially manufacturing at low cost a vegetable-fiber-material made food container of practical strength includes the steps of: forming a board of a predetermined size from pulp and at least one kind of vegetable fiber material other than the pulp; coating the board with thermoplastic resin having a heat sealing property; providing cuts at four corners of the board to form sidewall pieces; and hot-pressing the board thus obtained using a pair of press dies to form the food container, the pair of dies being composed of female die and male die, wherein one of the pairs of opposing sidewall pieces is arranged to be erected prior to the other pair of opposing sidewall pieces and four corners are bonded correspondingly to each other by a hot press process in order to form the container.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method of manufacturing a food container formed of vegetable fiber material, more specifically, to a method of manufacturing the food container formed of the vegetable fiber material commercially at low cost.

2. Related Background of the Invention

Conventional food containers for containing food, such as lunch boxes or trays, are made of plastic materials like foamed polyeurethane and so on. However, since the plastic materials have a problem in disposing them after use, vegetable-fiber-made food containers are strongly required in view of the environment conservation.

However, there has been a problem in manufacturing the vegetable-fiber-made food containers by die molding process that only shallow containers with insufficient strength could be manufactured. Further, in the case of the containers made from pulp board, there has been a problem of costly manufacturing, since the containers are so manufactured that cuts are formed at four corners, sidewall pieces are erected, edges of the sidewall pieces are brought into superposition to each other to apply bonding agent, and the bonded portions are manually fixed. As a consequence thereof, the vegetable-fiber-made food containers are not widely diffused comparing to the other food containers, e.g., cheap trays as presently sold in supermarkets.

Meanwhile, with regard to paper as vegetable-fiber-made material, the natural forest including the virgin forest is to be deforested for raw material of paper. However, it is a current issue to deforest the natural or virgin forest not only from view point of natural ecosystem where various animals inhabit but also from local environmental disruption view point.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a method of manufacturing a vegetable-fiber-material made food container which has a practical strength and can be manufactured commercially at low cost.

Another object of the present invention is to provide a method, considering a problem as to a global environment, of manufacturing the vegetable-filer-material made food container at low cost, capable of reducing an amount of pulp to be used therefor.

The above stated objects can be achieved with the present invention by employing the steps of: forming a board having a predetermined size of pulp and at least one kind of the vegetable fiber material other than the pulp; coating thermoplastic resin having heat sealing property onto the board; providing cuts for forming sidewall pieces at four corners of the board; and forming the food container with thus obtained board subjected to a hot press process with a pair of press dies, male and female dies, in which a pair of the sidewall pieces opposing to each other are arranged to be erected prior to another pair of the sidewall pieces opposing to each other.

It is specifically preferable to apply the thermoplastic resin having the heat sealing property onto one of the surfaces (either one of a front or rear surface) of the board for the purpose of coating, since it can be cost effectively substituted for plastic material and is printable thereon. Practically, if the coating is provided on both sides of the board, it becomes more expensive than using the plastic material in the current technique, which does not allow substitution for plastic material.

It is preferable for each of the cuts to be formed in such a fashion that a top angle section or a cut line reaches a corner of a bottom surface of the container to be formed. It is more preferable for each of the cuts to be formed into V-shape at an angle between 20 degrees and 60 degrees.

It is further preferable for each of the cuts to be formed into a funnel shape or a substantially Y-shape since a water leakage from inside a corner can be prevented effectively. Especially, when the container contains something which may cause the water leakage, the above stated configuration is effective.

Such an arrangement that a protruded portion is formed at one of the opposing sections of an opening periphery of the female die so that the pair of opposing sidewall pieces placed on the protruded portion is erected earlier than the other pair of the opposing sidewall pieces can make it possible to manufacture food containers at commercially low cost, four corners of containers being attached together through the hot press process using dies.

In a case of manufacturing the container with a sword guard shaped section, the opposing protruded portions are configured so as to be away from the concaved periphery of the female die at least by a distance corresponding to the sword guard shaped section of the container to be formed.

Providing guides for holding side edges of the board on the opposing protruded portion or at an adjacent position thereof facilitates positioning of the board for forming the container. Providing a guide abutting one of the other side edges of the board at the other opposing side edges of the board of the concave periphery of the female die further facilitates positioning of the board.

Before the pressing process, if one pair of the opposing sidewall pieces, which are arranged to be erected prior to the other pair of the opposing sidewall pieces, is bent, conventional dies can be employed to manufacture the container. However, when considering the productivity of the container, the above stated arrangement will be more preferable to produce the container.

It is preferable that the pulp and at least one kind of the vegetable fiber material other than the pulp are made of mixture of the pulp and the vegetable fiber material other than the pulp in view of the protection of the global environment destruction due to deforestation.

It is preferable that the vegetable fiber material other than the pulp be made of reed, sugar cone or kanaf.

It is preferable that a rate of the pulp and the vegetable fiber material other than the pulp be adjusted so that the vegetable fiber material other than the pulp is between 20 and 80 wt % with respect to the pulp. The less degrees, the less effect to the protection of the global environment, and the more degrees, the less strength and the less adhesive ability of an adhering section.

It is preferable to employ polyethylene or polypropylene as the thermoplastic resin having the heat sealing property according to the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view illustrating a state of a food container according to the present invention before pressing process.

FIG. 2 is a plan view illustrating a state of another food container according to the present invention before pressing process.

FIG. 3 is a plan view illustrating a state of another food container according to the present invention before pressing process.

FIG. 4 is a plan view illustrating a state of another food container according to the present invention before pressing process.

FIG. 5 is a perspective view illustrating an example of the food container manufactured by a method according to the present invention.

FIG. 6 is a perspective view illustrating an example of a female die to be used in the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Next an embodiment of the present invention is described.

The present invention is composed of the following processes.

(1) The board of the predetermined size is formed of the pulp and at least one kind of the vegetable fiber material other than the pulp.

(2) Thermoplastic resin having the heat sealing property is applied to the board.

(3) Cuts are formed at four corners of the board in order to form sidewall pieces.

(4) Thus obtained board is subjected to the hot press process using a pair of press dies, male and female in order to form the food container.

The process (1) can be performed by a known method of manufacturing the board from pulp. More specifically, the board is obtainable through the processes that pulp suspended in water is subjected to a sheet-forming process, followed by a water-squeezing process and drying process. The board obtained in the above processes is cut, if required, into a square shape of the predetermined size, and, preferably, into the square shape having R-shapes at four corners thereof as shown in FIGS. 1 to 4. It is preferable that the board contain water proof agent. Further, in the case of containing food which weeps oil, it is preferable for the board to contain oil proof agent in addition to the water proof agent.

As the vegetable-fiber-made material other than the pulp used in the present invention, it is preferable to use reed, sugar cone or kanaf. More specifically, using the reed is preferred since it is excellent in strength of the resultant container.

In the present invention, it is preferable to use a mixture of the pulp and the vegetable fiber material other than the pulp in view of the protection of the global environment due to the deforestation.

As to the rate of the pulp and the vegetable fiber material other than the pulp, it is preferable that the vegetable fiber material other than the pulp be between 20 and 80 wt %, more preferably between 30 and 60 wt %. The less addition of the vegetable fiber material, the less effect in protection of the global environment, while the more addition of the vegetable fiber material, the less strength and the more tendency of abruption of the bonding section.

The process (2) in which the thermoplastic resin having the heat sealing property is applied to the board in a coating manner may be done after a formation of the cuts or may be done before the formation of the cuts; however, the coating process is done before the formation of the cuts in the present embodiment. The thermoplastic resin is preferably applied to either surface, front or rear, of the board. If the thermoplastic resin is applied to both surfaces, diffusion of the container according to the present invention will be adversely effected for the reason of an expensiveness of the container at present and further no printable surface is obtained. In addition, the thermoplastic resin is preferred to be applied to the surface on which the food is placed. The reason for applying coating on the surface on which the food is placed is that the coating prevents juice or the like from infiltrating into the container. As the thermoplastic resin, it is preferable to use especially polyethylene or polypropylene.

A content of the thermoplastic resin differs depending on the kinds of the thermoplastic resin. Here, a range between 2 and 10% with respect to a mass of the board, more preferably, between 3 and 6% with respect to the mass of the board. Here, the “content” is represented by a percentage of the “mass of the heat sealing agent to be applied to the board” with respect to the entire mass of the board of which one surface is applied with the thermoplastic resin.

The cuts formed in the process (3) may be just formed into cut lines; however, it is preferable for the cuts to be formed into V-shapes at an angle equal to or less than 90 degrees or, more preferably, between 20 degrees and 60 degrees as shown in FIG. 1.

FIG. 1 illustrates an example of forming the cuts 1 in accordance with the process (3) in which the board formed into a square shape (rectangular shape) with round corners at four corners is provided with cuts 1 having V-shapes and a state is shown that long sidewall pieces 3, 3′ and short sidewall pieces 4, 4′ are provided consecutively on the bottom surface 2. Note that, reference numeral 5 in FIG. 1 represents concave portions formed continuously between the bottom surface 2 and the sidewall pieces 3, 3′ and 4, 4′, which are formed by the pressing process using dies in order to increase the strength of trays to be manufactured, which however is not yet formed in this stage. In this stage, the board is actually as shown in FIG. 4.

FIG. 2 illustrates another example of forming the cuts in accordance with the process (3), in which cuts 1 a are so formed that the V-shaped notches 1′ are consecutively provided with the prolonged cut lines 6 to finally reach the corners of the bottom surfaces 2, resulting in having an appearance of substantially y-shapes (a small letter of y). With such a configuration, areas overlapping each other at both ends of the sidewall pieces 3, 3′ and 4, 4′ adjacent to the bottom surface 2 can be large; therefore the water leakage from the corners can be avoided effectively.

FIG. 3 illustrates another example of forming the cuts in accordance with the process (3), in which V-shaped notches 1″ of small angles are consecutively provided from upper bases (bottom ends) of the tranpezoidal notches 7 to the corners of the bottom surface 2 in order to finally form funnel shaped or substantially Y-shaped cuts 1 b. With such a configuration, areas overlapping each other at both ends of the sidewall pieces 3, 3′ and 4, 4′ adjacent to the bottom surface 2 can be large, therefore the water leakage from the corners can be avoided effectively.

FIG. 4 illustrates another example of forming the cuts in accordance with the process (3), in which cuts 1 c are so formed that the cut lines 6′ are consecutively provided from the notches 1″ of round V-shape to the corners of the bottom surface 2, in order to finally form substantially Y-shapes (a large letter of Y). In the embodiment as shown in FIG. 2, the cut line 6 extends from one of the lines of the V-shaped cuts; however, in the embodiment as shown in FIG. 4, the cut line 6′ is a bisector of the angle of the V-shaped cut.

In the embodiment as illustrated in FIG. 2, the cut line 6 may be provided with a small clearance. In the embodiment as illustrated in FIG. 3, each of the V-shaped notches 1″ may be a cut line. Further, regarding the expressions in the present specification as to V-shape, Y-shape and funnel shape, the shapes are not necessarily defined precisely in such shapes but may be substantially such shapes. In short, the shapes of the notches should not be strictly defined as far as the top angle portions or the cut lines of the notches reach corners of the bottom surface 2.

In order to form the food container by means of a pair of hot press dies consisted of the male die and the female die in accordance with the process (4), one of the pairs of the opposing sidewall pieces of the board on which cuts are formed as illustrated in FIGS. 1 to 4 is erected prior to the other pair of the opposing sidewall pieces and the board thus formed is placed in the female die to be subjected to a hot pressing process by the upper male die in order to form the container, and simultaneously, the board is subjected to the heat sealing process in order to bond the sidewall pieces at the four corners correspondingly each other. Then, as shown in FIG. 5, the container 8 is so formed that corner sections 13 at the four corners have round shapes.

Either pair of the opposing sidewall pieces may be erected prior to the other pair; however, it is preferable for the pair of short sidewall pieces 4, 4′ to be erected prior to the other pair since it is easier. If the sidewall pieces are preliminary erected by means of a paper folding machine, a conventional press dies can also be utilized to form the container.

FIG. 6 illustrates an example of a female die (concave die) 9 to be used in manufacturing according to the present invention, in which opposing sections at short side surfaces of the upper periphery of the concave section 10 of the female die 9 are provided with rods 11, 11′ having square shapes in cross section in a manner opposing to each other and slightly spaced from the concave section 10. On the rods 11, 11′, guiding boards 12, 12′ are provided to stand thereon. At a backside of the concave section 10 of the female die 9, a guiding board 12″ is provided to stand thereon.

The board illustrated in FIG. 4 is placed so that the pair of short sidewall pieces 4, 4′ is held between the guiding plates 12, 12′ and one of the long sidewall pieces 3 (or 3′) is abutted on a guide plate 12″ via the rods 11, 11′ on the concave section 10 of the female die 9. Then, the male die (convex die which is not shown in FIG. 6) is descended and brought into fit with the concave section 10 of the female die 9 from the above to be subjected to the hot pressing process.

Accordingly, the pair of the opposing sidewall pieces 4, 4′ is erected prior to the other pair of the opposing sidewall pieces 3, 3′, and then the container as shown in FIG. 5 can be manufactured in a single step by a complete fitting and the hot pressing process. Note that, as shown in FIG. 5, the sword guard shaped section 14 provided at an upper edge and the concave sections 5 of the container are formed by the hot pressing process using the male and female dies.

In order to form the sword guard shaped section 14 on the upper edge of the container, as shown in FIG. 6, the rods 11, 11′ are away from the both side ends of the concave section by the distance corresponding to the sword guard shaped section. The concave section 10 may include steps formed thereon, and the male die is formed into a shape including the steps so as to fit into the concave section. The sword guard shaped section may be obviously formed utilizing the steps at which the female die and the male die are closely contacted with each other.

A cover can be consecutively formed with the container of the present invention. In the case of forming the consecutive cover, the cover may be formed consecutively with the sidewall piece (preferably with either one of the sidewall pieces 3, 3′) as shown in FIGS. 1 to 4.

As shown in FIG. 5, corner sections 13 at four corners are thick because portions of the board are superimposed each other, consequently portions of the female die and/or the male die at which the corner sections are formed are preferred to be thinned by that amount.

The food containers manufactured by the method according to the present invention are not limited to, but are suitable for the use of lunch boxes, fermented soybeans containers, trays, covers of the lunch boxes, and the like.

According to the present invention, the food container formed of the vegetable-fiber-made material and having practical strength can be produced commercially at low cost, therefore the container according to the present invention is sufficient enough as an alternative to the food container made of plastic, resulting in remarkably contributing to the environment protection.

Further, according to the present invention, a food container, being formed of vegetable fiber material which is cheap and uses reduced amount of pulp, can be obtained, thereby contributing to protection of the global environment destruction due to deforestation. 

1. Manufacturing method of food containers or covers thereof comprising the steps of: forming a board of a predetermined size from pulp and at least one kind of vegetable fiber material other than the pulp; coating the board with thermoplastic resin having a heat sealing property; providing cuts at four corners of the board to form sidewall pieces; and hot-pressing the board thus obtained using a pair of press dies to form food containers or covers of the containers, a pair of dies being composed of female die and male die; wherein one pair of the opposing sidewall pieces is arranged to be erected prior to the other pair of opposing sidewall pieces.
 2. The manufacturing method as claimed in claim 1, wherein said thermoplastic resin having the heat sealing property is applied to one of surfaces of the board to provide coating thereon.
 3. The manufacturing method as claimed in claim 1, wherein each of the cuts is formed so that a top of an angled section or a cut line reaches a corner of a bottom surface of the container to be formed.
 4. The manufacturing method as claimed in claim 3, wherein each of the cuts is formed into V-shape at an angle between 20 and 60 degrees.
 5. The manufacturing method as claimed in claim 3, wherein the cuts are formed into funnel shapes or substantially Y-shapes.
 6. The manufacturing method as claimed in claim 1, wherein one pair of opposing sections of a concaved periphery of the female die is provided with a pair of protruded portions, and one pair of opposing sidewall pieces of the board placed on a pair of protruded portions are formed so as to be erected prior to the other opposing sidewall pieces.
 7. The manufacturing method as claimed in claim 6, wherein the opposing convex sections are away from the concave periphery of the female die by at least a distance corresponding to a sword guard shaped portion of the container to be formed.
 8. The manufacturing method as claimed in claim 7, wherein guides for holding side edges of the board is provided at the opposing protruded portions or at adjacent positions thereto.
 9. The manufacturing method as claimed in claim 8, wherein one of the other opposing surfaces of the concave periphery of the female die is provided with a guide to which one of the other side edges of the board abuts.
 10. The manufacturing method as claimed in claim 1, wherein one pair of the opposing sidewall pieces is bent before performing the pressing process, and arranged to be erected prior to the other pair of the opposing sidewall pieces.
 11. The manufacturing method as claimed in claim 1, wherein the pulp and at least one kind of the vegetable fiber material other than the pulp is a mixture of the pulp and the vegetable fiber material other than the pulp.
 12. The manufacturing method as claimed in claim 11, wherein the vegetable fiber material other than the pulp is reed, sugar corn, or kanaf.
 13. The manufacturing method as claimed in claim 12, wherein a rate of the pulp and the vegetable fiber material other than the pulp is defined such that the vegetable fiber material other than the pulp is between 20 and 80 wt % with respect to an entire mass of the board.
 14. The manufacturing method as claimed in claim 1, wherein the thermoplastic resin having the heat sealing property is polyethylene or polypropylene. 